Bone ash
Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide, 42.39% phosphorus pentoxide, and 1.79% water. The exact composition of these compounds varies upon the type of bones being used, but generally the formula for bone ash is: Ca5(OH)(PO4)3. Bone ash usually has a density around 3.10 g/mL and a melting point of 1670 °C (3038 °F). Most bones retain their cellular structure through calcination.
The raw material for bone china is about 50% bone ash derived from animal bones. These bones undergo multiple processing stages during which all meat is removed and the bone is completely cleaned. Once cleaned, the bone is heated to about 1000 °C (1832 °F) so that all additional organic material is removed from the bone and the bone becomes sterilized. Lastly, the newly sterilized bone is ground with water into fine particles which can be used as a raw material for bone china. Bone ash plays an important role in the creation of bone china, as the phosphate of the bone generates beta tricalcium phosphate, and other compounds from the bone create a calcium crystal called anorthite. Synthetic alternatives dicalcium phosphate and tricalcium phosphate are used as substitutes for bone ash. Most bone china are produced with synthetic alternatives rather than bone ash.
Bone ash can be used alone as an organic fertilizer or it can be treated with sulfuric acid to form a "single superphosphate" fertilizer which is more water soluble:
Similarly, phosphoric acid can be used to form "triple superphosphate", a more concentrated phosphorus fertilizer which excludes the gypsum content found in single superphosphate:
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